Method of removing metals from petroleum hydrocarbons



E. C. GOSSETT Jan. 7, 1964 METHOD OF REMOVING METALS FROM PETROLEUM HYDROCARBONS 7 Filed March 17, 1960 FEED RESERVOIR W/THDRAWAL PORT PORT CAP C OOLANT OUT VENT PORT

PORT

COOLANT IN FEED INVENT OR EARL C GOSSETT Magma/9&1 a

ATTQRNEYS United States Patent 3,117,078 METHDD 6F REMOVING METALS FROM PETROLEUM HYDRQCONS Earl C. Gossett, South Holland, lll., assigncr, by mesne assignments, to Sinclair Research, 116., New York, N.Y., a corporation of Delaware Filed Mar. 17, 1960, Ser. No. 15,646 3 Claims. (Cl. 20825l) This invention relates to a method for the preferential separation of metals contained in high boiling petroleum hydrocarbons through the use of thermal diffusion.

'It has been known for some time that it is possible to separate, by thermal difiusion, liquids and gases that are incapable of separation by any other known method, or that are separated by other methods with great ditficulty. The process of thermal difiusion consists in essence of confining a fluid mixture in a narrow chamber and imposing across the chamber a temperature gradient. When the opposed walls defining such a chamber are non-horizontal, thermal circulation of the contents of the chamber is set up by virtue of the difierences in conditions and molecular structure of the separate fluid components adjacent the relatively heated and cooled walls, commonly referred to as the hot and cold walls. This results in convection currents which facilitate certain separations.

It has now been found that the thermal diffusion process of separation is an effective means for the preferential separation of metals, such as vanadium and nickel, contained in petroleum hydrocarbon feed materials. In accordance with my method, the metal-containing petroleum feed-stock is introduced into a thermal dififusion chamber comprising opposed, non-horizontal or essentially vertical walls and a temperature gradient is imposed on the :feed material in the chamber by having the opposed walls at different temperatures such as by relatively heating one of the walls and/ or relatively cooling the other. The feed in the chamber resolves into fractions, the lower fractions containing a substantially increased concentration of nickel and/or vanadium and the upper fractions having a substantially reduced vanadium and/or nickel content as compared with the feed. Upper and lower fractions are then separately withdrawn.

.The petroleum feed material of the present invention can be any petroleum hydrocarbon fraction boiling primarily in a range above about 500 F. and having a significant soluble nickel and/ or vanadium content. The feed may include material that boils below 500 =F., and this component is usually a minor portion of the feed, frequently up to about 5%. Ordinarily the nickel and vanadium contents, calculated as nickel oxide and vana dium oxide, in these fractions will each be at least about 0.2 part per million based on the feed, usually at least about 1 part per million. There is no real upper limit on the boiling point of the feed material of the present invention as long as it can be made liquid at treating temperatures; some fractions having, for example, up to about or more of the fraction boiling above 1000 F. Suitable feed materials include, for example, heavy residual oils, catalytic cracking stock such as gas oils from, for instance, vacuum flashing, vis breaking, deasphalting, etc. The feedstoeks of the present invention do not include refined lubricating oils or cycle oils which do not contain significant nickel or vanadium contarninants.

The invention will be described by references to the drawings in which FIGURE I is a diagrammatic side view of one form of apparatus in which the method of the present invention can be carried out.

lFIGUR-E ll represents a detailed vertical section of a portion of 'FEGURE I in which electrical means is used to heat the hot wall. It should be understood that the drawings represent but one form of apparatus in which the method of the present invention can be carried out and should not be construed as limiting.

The apparatus illustrated in FIGURE I comprises a tube 3 disposed concentrically within an outer tube 5. Tube 3 forms the cold wall of the apparatus and tube 5 the hot wall. Any suitable means may be provided for relatively heating and cooling the walls. Thus, for example, the hot wall may be heated by means of electrical windings '7 (see FIG. 11), or by circulating heating fluid through an outer wall jacket, etc. and the cold wall by circulating a coolant such as water through inner tube 3. if desired this arrangement can be reversed by relatively simple modifications tomake the outer tube 5 the cold wall and inner tube 3 the hot wall. The inner wall 3 and outer wall 5 define a thin annular space 9 (see FIG. II) which constitutes the thermal diffusion chamber. Outer wall 5 is provided with several ports 20 for withdrawal of fractions and a vent port 21 at the extreme top.

In one operation all ports are closed except the vent port and a port 22 designated as the feed entry port preferably the middle port. The feed of the present invention contained in feed reservoir 13 is introduced into annular space 9 (see HG. H) by means of line 15' and the feed entry port 17. If desired the feed may be introduced at several points through the ports. With the introduction of the feed, a temperature gradient is imposed across the thermal difiusion chamber or annular space by relatively heating one of the inner or outer walls and relatively cooling the other. Generally the feed introduction is below the demetallized product take off, preferably between the demetallized product and metal containing fractions which is usually the approximate middle of the column. One or more upper fractions produced are withdrawn via the upper withdrawal ports and one or more bottoms fractions via the bottom or lower withdrawal ports.

The temperatures for the hot and cold walls are selected to provide a significant temperature gradient across the thermal diffusion chamber. However, Wall temperatures should be chosen that will provide a reasonably large temperature gradient across the thermal diffusion chamber without either wall temperature being so low as to impede free flow or so high as to exceed the boiling point or cracking temperature of the feed material. Preferably the difference in temperatures should be at least 50 F.; the greater the difference the better to minimize process time. The present invention would normally encompass temperatures in the range of about to 650 F. or more.

A significant variable in thermal diffusion is the Width of the space between the hot and cold walls. The width must be narrow so that a high temperature gradient per unit of distance will be obtained but if it is too narrow 3 the capacity of the unit may be too low. In the method of the present invention a width of about 0.005 to 0.1 inch can be employed with effective results.

The following example is given to further illustrate the present invention.

Example A gas oil derived from vacuum flashing and having an initial boiling point of 450 F. and a 90% distillation point of 1000 "F. (about 5% of the feed boiling below 650 F.) was subjected to metals analysis and introduced into the apparatus of FIGURE I. The concentric tubes of the apparatus were about 6 feet high and the Width of annular space formed by the tubes was about 0.015. The hot wall was heated by electrical windings as shown in FIGURE H and contained a total of 10 withdrawal ports, vertically spaced, including the vent port.

The following procedure was used for filling the diffusion column:

All ports were closed except the vent and a flexible tubing run from the feed reservoir to the middle port. A pinch clamp was placed on the tubing directly adjacent the port. The pinch clamp was then opened and the feed was introduced into the annular space until it drained from the vent port. The vent port was closed, the electrical heating means for the hot Walt was turned on and the circulation of cooling water for the cold wall started. The hot wall temperature was controlled at the bottom of the column at 300:10" F. and the cooling water exit temperature was maintained at 175110" After conditioning for one hour, the vent was opened to release entrapped air or gas. The vent was again closed and the feed line to the column was allowed to remain open throughout the run. After a period of about 96 hours, the feed reservoir was blocked off by pinching the clamp and fractions were withdrawn from the 5 top ports including the vent port and composited. Likewise, fractions were withdrawn from the lower 5 ports and composited.

In order to obtain sufficient samples for metals testing, a second run was made in the same manner. In this separation the hot wall temperature was controlled at the middle of the column at 30 -10 -F. with the cooling water exit temperature the same as that of the first run. The top cuts of the second run were withdrawn and composited with the 5 top cuts of the first run. Similarly, the five bottom cuts of the second run were withlvIETALS CONTENT, P.P.l\'[.

Charge to Column 1.80 4.1.0 Top Composite 0.17 0.25 Bottom Composite 43 7. 05

The data clearly demonstrates that the method of the present invention effectively concentrates nickel and vanadium metals in the bottom cuts.

1 claim:

1. A method for the separation of metal selected from the group consisting of nickel and vanadium contained in hydrocarbons boiling primarily above about 500 P. which comprises providing said liquid hydrocarbon in an essentially vertical thermal ditfuson zone, imposing a temperature gradient across the hydrocarbons in the zone, whereby hydrocarbon fractions are formed in said zone, a lower fraction containing a substantially increased concentration of said metals, and an upper fraction being substantially reduced in said metals content, and separately withdrawing the lower fraction and upper fraction.

2. The method of claim 1 wherein the temperature gradient is at least 3. The method of claim 1 wherein the thermal diffusion zone has a width of about 0.005 to 0.1 inch.

References Cited in the file of this patent UNITED STATES PATENTS Birchfield Dec. 6, 1960 OTHER REFERENCES 

1. A METHOD FOR THE SEPARATION OF METAL SELECTED FROM THE GROUP CONSISTING OF NICKEL AND VANADIUM CONTAINED IN HYDROCARBONS BOILING PRIMARILY ABOVE ABOUT 500* F. WHICH COMPRISES PROVIDING SAID LIQUID HYDROCARBON IN AN ESSENTIALLY VERTICAL THERMAL DIFFUSION ZONE, IMPOSING A TEMPERATURE GRADIENT ACROSS THE HYDROCARBONS IN THE ZONE, WHEREBY HYDROCARBON FRACTIONS ARE FORMED IN SAID ZONE, A LOWER FRACTION CONTAINING A SUBSTANTIALLY INCREASED CONCENTRATION OF SAID METALS, AND AN UPPER FRACTION BEING SUBSTANTIALLY REDUCED IN SAID METALS CONTENT, AND SEPARATELY WITHDRAWING THE LOWER FRACTION AND UPPER FRACTION. 